A man will face court after allegedly using a nail-studded piece of wood to attack and seriously injure his girlfriend's brother in Sydney's south.

Police say the attack happened at a Peakhurst Heights property at about 1pm on Friday during an argument between a 33-year-old man and a 42-year-old man.

The younger man allegedly struck the older man in the face with a piece of wood which had nails protruding from it, causing a deep laceration.

The victim was taken to St George Hospital for treatment.

The 33-year-old was arrested nearby and was refused bail to appear in Parramatta Court on Saturday, charged with wounding a person with intent to cause grievous bodily harm (domestic violence related).